JPH0327088B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical element in which the relative position of two optical surfaces can be varied.

Such optical elements in which the relative positions of two optical surfaces are variable, such as variable apex prisms and variable thickness parallel flat plates, are useful for focusing, vibration-proof optical systems, etc.; The known types include those in which liquid is sealed between two parallel flat glasses, and those in which liquid is sealed in a rubber membrane and deformed under pressure by sandwiching it between two parallel flat glasses. be. However, these methods all use liquid and require a liquid reservoir and a pressurizing device, which poses many problems in terms of miniaturization and manufacturing.

There are also methods that use piezoelectric elements as the medium, but they have the disadvantage of a small amount of deformation.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate these drawbacks and provide an optical element that has a simple configuration, has a large variation, and is capable of changing the relative positions of two optical surfaces.

The optical element of the present invention includes a pair of optical members selected from lenses or flat optical members, and a light-transmitting elastic body held between the pair of optical members, The present invention is characterized in that the apex angle is made variable, and the angle formed by the optical axes of the pair of optical members changes in response to a change in the apex angle.

Further, the optical element of the present invention includes a pair of lenses,
and a light-transmitting elastic body held between the pair of lenses, and at least one of the lenses is configured to be movable in a direction orthogonal to the optical axis.

Furthermore, the optical element of the present invention includes a first optical member, a second optical member, and a third optical member, all of which are arranged in order and have a flat plate shape, and the first optical member and the second optical member.
a light-transmissive first elastic body held between the optical members;
a light-transmissive second elastic body held between the second optical member and the third optical member, and the distance between the first optical member and the second optical member, and the second
The distance between the optical member and the third optical member is variable, and the dispersion characteristics of the first elastic body and the dispersion characteristics of the second elastic body are different from each other.

Further, the optical element of the present invention includes a first optical member and a third optical member each having a flat plate shape, and a curved second optical member disposed between the first optical member and the third optical member. , the first optical member and the second optical member
a light-transmissive first elastic body held between the optical members;
a light-transmissive second elastic body held between the second optical member and the third optical member, and the distance between the first optical member and the second optical member, and the second
The distance between the optical member and the third optical member is variable, and the dispersion characteristics of the first elastic body and the dispersion characteristics of the second elastic body are different from each other.

The present invention will be explained in detail below using the drawings.

FIG. 1 is an example of an optical element in which the apex angle formed by two optical surfaces can be changed by deforming an elastic body.

Reference numeral 1 designates an elastic body, and 2 and 3 designate parallel flat glass plates as optical members, the end points 2' and 3' of which are fixed, and the other end points 2'' and 3'' are movable by application of external force.

Figure 1 a shows a state where no pressure is applied to points 2″ and 3″, and the first
Figure b shows a state where points 2'' and 3'' are pressurized in the direction of the arrow. In this way, by applying pressure to the end points 2'' and 3'', the elastic body 1 is deformed, and the apex angle of the prism changes from θ ₀ to θ. At this time, by using a material as described below as the elastic body 1, it is possible to obtain a large amount of change in the prism apex angle with a small external force.

The optical element according to the present invention can make the imaging position variable by relatively changing the positions of two optical surfaces sandwiching an elastic body. The direction of variation of the position of the optical surface can be done arbitrarily. For example, it can be varied so that it has components in both directions parallel to or perpendicular to the optical axis, or both parallel and perpendicular.

Figure 2 is an example. Lenses 4 and 5 are optical members, and the lens 5 is movable in a direction perpendicular to the optical axis.

FIG. 2a shows a state in which the lens 5 does not move, and FIG. 2b shows a state in which the lens 5 moves in a direction orthogonal to the optical axis. As shown in the figure, by moving the lens 5,
Since the images formed by the lenses 4 and 5 can be moved in a direction perpendicular to the optical axis, such an element is useful for anti-vibration optical systems that prevent image movement due to shaking of TV cameras and the like.

Next, materials effective as the elastic body used in the present invention will be explained.

The elastic body used in the present invention is one that has the property (elasticity) that it deforms when force is applied to the object, and that the deformation returns to its original state when the force is removed, as long as the applied force is not too large (within the elastic limit). can be used.

In a normal solid, the maximum strain (critical strain) within its elastic limit is about 1%. In addition, vulcanized elastic rubber has a very large elastic limit, and its limit strain is close to 1000%.

In the optical element according to the present invention, an elastic modulus depending on the characteristics of the optical element to be formed is appropriately used, but in general, in order to easily obtain large elastic deformation, or the state after deformation is optically homogeneous. In order to achieve this, it is preferable to use a material with a small elastic modulus.

In addition, the elastic modulus G is G=p/r (p=stress, r=
elastic strain). Further, elasticity that causes large deformation with small stress is called high elasticity or rubber elasticity, and therefore, this type of elastic body can be particularly preferably used in the present invention.

Generally speaking, “rubber” is used as such a rubber elastic body.
Natural and synthetic rubbers known as styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), ethylene propylene rubber (EPM, EPDM), butyl rubber (IIR), chloroprene rubber (CR) , acrylonitrile-butadiene rubber (NBR), urethane rubber (U), silicone rubber (Si), fluorine rubber (FPM), polysulfide rubber (T), polyether rubber (POR, CHR, CHC), etc. can. Among them, ethylene propylene rubber and silicone rubber, which are transparent to visible light, are highly effective. All of these exhibit a rubbery state at room temperature. However, in general, polymeric substances take either a glass state, a rubber state, or a molten state, depending on the degree of Brownian motion of the molecules. Therefore, a wide variety of polymeric substances exhibiting a rubbery state at the operating temperature of the optical element can be used as the elastic body of the present invention. The elastic modulus in the rubber state is mainly determined by the crosslinking state of the polymer chains that make up the elastic body, and therefore, for example, vulcanization of natural rubber is nothing but a process that determines the elastic modulus.

In the present invention, it is desirable that the elastic body used be able to undergo large deformation with small stress, and for this purpose, it is important to adjust the crosslinking state.

However, a decrease in the elastic modulus (a tendency for large deformations to occur with small stress) also leads to a decrease in strength. It is necessary to select the body appropriately.

The elastic modulus is also measured by, for example, tensile, bending, or compression methods, depending on the type of stress depending on the usage of the optical element.

The elastic body used in the present invention has an elastic modulus smaller than that of a normal solid, 10 ¹ to 10 ¹³ dyne/cm ² , and preferably 10 ⁸ dyne/cm ² or less of a rubber elastic body.
10 ⁶ dyne/cm ² or less, particularly preferably 5×
The lower limit is 10 ⁵ dyne/cm ² or less, and the smaller the lower limit is, the better, as long as the elastic body does not spill when the elastic body constitutes an optical element, unlike a normal liquid. Note that although optical elements are often used at room temperature, they may also be used at particularly high or low temperatures, so the above range of elastic modulus is at the operating temperature of the optical element.

The hardness and softness of an elastic body depend to some extent on its elasticity. JISK6301 stipulates a method of applying a small strain to the sample surface using a spring, and evaluating the hardness of rubber based on the degree of penetration, which can be easily determined.

However, when the elastic modulus is as low as 10 ⁶ dyne/cm ² or less, measurement cannot be performed using the above method, and in that case, the penetration is evaluated using a 1/4 inch micro-consistency meter according to JISK2008.

In addition, if the elastic modulus is small, it is difficult to measure it with "tensile extension" as a measurement method, so compression (5
% deformation), and its value can be determined and its correspondence with the previous penetration degree can be determined.

Rubber elastic bodies are manufactured using the conventional vulcanization (crosslinking) process.
In addition to those that do not require vulcanization, such as ethylene-vinyl acetate copolymers and A-B-A type butadiene-styrene block copolymers, and chain polymers, etc. (by controlling the molecular chain length).

In all of these, the elastic modulus is controlled by adjusting the crosslinking state, the combination of molecules in the block copolymer, the gel state, etc.

Further, in addition to controlling the elastic body depending on the structure of the elastic body itself, it is also possible to change and adjust its properties by adding a diluent or a filler.

For example, silicone rubber (manufactured by Shin-Etsu Chemical;
When KE104 (trade name) and a catalyst (trade name: AT-104 manufactured by Shin-Etsu Chemical Co., Ltd.) are added, as the amount added increases, the hardness and tensile strength decrease, and conversely, the elongation increases.

Such materials can have various elastic moduli depending on their crosslink densities, and when a particularly large amount of deformation is desired, it is effective to use them in a gel state with a low crosslink density. It is also possible to change the refractive index and dispersion by mixing various substances.

Next, a manufacturing method useful for the optical element of the present invention will be explained.

The first method is to form the elastic body in advance into a shape similar to the shape it would have when no external force is applied, and then bond parallel flat glass or lenses as shown in FIG. 1 or 2.

Second, a lens or parallel flat glass is placed in a lens barrel or a suitable container in advance, and a liquid monomer is poured into the gap.
A method of casting is also possible.

Thirdly, there is a method in which the vicinity of the surface of an elastic body having a predetermined shape is hardened and used as an optical surface. for example,
After a monomer is injected into a container of a predetermined shape and polymerized to some extent by casting, the vicinity of the surface is subjected to a curing treatment such as ultraviolet irradiation. In addition, a hardened layer is first formed along the inner wall of the container,
Casting molding can also be performed inside the hardened layer.

Next, a method for driving an optical element according to the present invention will be explained. The optical element in the present invention is basically easily driven by applying an external force to its optical surface, another surface other than the optical surface, or the inside of an elastic body.

The first method is to mechanically apply force using a screw, cam, etc., and is effectively used, for example, in an optical system shown in FIG. 3, which will be described later.

A second method is to use a piezo element, an example of which will be described later with reference to FIG.

The third method is to use an electromagnet, an example of which will be described later in FIGS. 7-9.

Further, as other methods, a stepping motor, volume change during sol-gel transition due to thermal expansion, temperature or PH change, or shape memory alloy can be used.

Next, aspects of other optical systems that effectively utilize the optical elements of the present invention will be described.

FIGS. 3 and 4 show an application to focusing of a photographic lens or the like or correction of chromatic aberration fluctuations when changing the magnification of a zoom lens by varying the distance between optical surfaces sandwiching an elastic body.

In FIGS. 3a and 3b, 6 is a normal lens system such as a photographic lens, 7 is an optical element in the present invention disposed between the lens system 6 and the image plane,
The optical element 7 in the present invention is composed of parallel flat glass glasses 8, 9, 10 which are optical members and elastic bodies 11, 12 having different dispersion characteristics.The parallel flat glass glasses 8, 10 are fixed to a lens barrel, The glass 9 is movable in the optical axis direction, and its position in the optical axis direction is determined by a helicoid, a cam, etc.
The optimal position is determined in conjunction with a focusing mechanism by extending the lens system 6 or a zoom mechanism by a cam. For example, elastic bodies 11, 12
It is assumed that the refractive indexes for the reference wavelength (eg, d-line) are the same N, and the refractive indexes for the sub-wavelengths (eg, g-line) are different, N' ₁ and N' ₂ , respectively. Then, as shown in FIG. 3a to FIG. 3b, when the parallel plate glass 9 moves, the optical path length for the reference wavelength does not change, but only the optical path length for the sub wavelength changes.
This can be used to correct longitudinal chromatic aberration.

Depending on the application, the parallel flat glass 8 or 10 may be movable or the elastic bodies 11, 1 may be movable.
By having different refractive indexes for the two reference wavelengths, it is possible to simultaneously provide a focusing function for the reference wavelengths. Also,
It is also possible to correct higher-order chromatic aberrations by giving the parallel flat glass 9 a curvature, as shown at 9' in FIG.

FIG. 5 shows an example in which an optical element consisting of a pair of lenses sandwiching an elastic body is used for focusing. 6 is a lens system such as a photographic lens as mentioned above;
Reference numeral 13 denotes an optical element, which consists of two plano-convex or plano-concave lenses 14 and 15 with their planes facing outward, and an elastic body 16 between them, and the elastic body 16 is deformed as shown in FIGS. 5a to 5b. However, by changing the distance between the two lenses, the imaging position can be made variable. At this time, the elastic body 16 and the lens 1
If the refractive indices of the two lenses 14 and 15 are close, the focusing function of the optical element 13 can be considered to be a change in the optical path length due to a change in the thickness of the parallel flat glass.
By selecting the refractive index, dispersion, etc. of the lenses 4 and 15 and the elastic body 16, aberration fluctuations during focusing can be corrected.

The optical element 13' shown in FIG. 6 is an example of the element shown in FIG. 5 in which both lenses 14 and 15 are curved. In FIG. 6, 14' and 15' are lenses having curvature on their outer surfaces, and 17 is a piezoelectric film made of polyvinyldenum fluoride, which deforms as shown in FIG. 6b when a voltage is applied. ' is moved in the optical axis direction to make the focal length of the combined system of lenses 14' and 15' variable.

A zoom lens changes the focal length of the lens system by changing the air distance between the lenses, but it is desirable in optical design that not only the air distance but also the lens thickness itself be variable. This is because changes in air spacing are accompanied by rapid aberration fluctuations.
Also, from the point of view of chromatic aberration correction, changes in the thickness of the lens medium itself having dispersion can be effectively utilized. From these points, the element shown in FIG. 6 is also useful as a component of a zoom lens or the like.

FIG. 7 shows an example of the configuration of an objective lens system for picking up an optical disk using the variable apex angle prism shown in FIG. 18 is a variable apex angle prism according to the present invention, which is made of parallel flat glass 20, 21 and an elastic body 22; 19 is an objective lens;
The incident laser beam is directed to the recording surface 25 of the optical disk.
image on top. The focused laser beam changes its polarization state according to the information written on the recording surface at that position, is reflected, travels the same optical path as when it was incident, and is detected by a detector that detects its polarization state. By detecting this, the recorded information is read out. FIG. 7a shows the state when the imaging plane of the laser beam moves above the recording surface, and FIG. 7b shows the state when it moves downward. Information on such optical disks is recorded concentrically, and the records are read out by rotating the optical disk, so the laser beam is always on the same circumference regardless of vibration or eccentricity of the optical disk. It is necessary to perform tracking to form an image of the beam, but conventional methods for tracking include mechanical movement of the entire objective lens or optical deflection using a galve anometer, which reduces the speed of response and the compact size of the device. There was a problem in terms of compatibility.

In the example shown in FIG. 7, tracking can be performed very easily by changing the apex angle of the variable apex angle prism as shown in the figure in accordance with the detected tracking error.

In FIG. 7, the parallel flat glass 20 sandwiching the elastic body 22 is fixed to the objective lens 19, and the parallel flat glass 21 is rotatable within the plane of the paper, which is the radial direction of the optical disk.
It is placed near the entrance pupil of No. 9. As shown in the figure, the apex angle of the variable apex angle prism changes due to the rotation of the parallel flat glass 21, and the incident laser beam is deflected so that it can always be imaged on the same circumference by the objective lens 19. The optical system shown in FIG. 7 can be used for recording and reading from various conventional recording members, such as magneto-optical disks and heat mode recording using light.

Figure 8 shows the variable apex angle prism 18 in Figure 7.
FIG. 8a is a front view and FIG. 8b is a back view. 23 and 23' are two independent electromagnets, and 24 and 24' are ferromagnetic materials such as iron plates.
By controlling the attractive force acting between -24 and between 23' and 24', the prism apex angle can be easily controlled. Furthermore, as shown in Figure 9, by providing three sets of electromagnets and ferromagnetic materials, it is possible to deflect the incident light two-dimensionally, and it is also possible to simultaneously control the imaging position in the circumferential direction, so-called jitter correction. It is possible. Furthermore, the element shown in FIG. 9 is also effective for two-dimensional optical scanning of minute objects such as microfilms.

In addition, in FIG. 7, the parallel plate glass 21 can be moved not only in the plane of the paper but also in parallel to the optical axis, and the incident beam is not parallel but focused or diverging light to improve the coupling in the optical axis direction. Image position control, that is, automatic focus adjustment function can also be added.

10a and 10b show the case where an element 26 is used in which the parallel flat glass 21 in FIG. 7 is replaced with a lens 27, which is an optical member. In this case, as in the example of FIG. 7, tracking can be performed by rotating the lens 27 in the plane of the paper, and focus adjustment can be performed by moving the lens 27 parallel to the optical axis direction as shown in the figure. Can be done.

FIG. 11 shows an example in which the present invention is applied to an anti-vibration optical system, in which the optical element 28 in the present invention is a lens 29,
31 and an elastic body 30, 32 is a lens barrel, 33 is a sensor surface of an image pickup tube, etc., and 31 and 33 are fixed to the lens barrel 32. Assume that when an object is imaged on the sensor surface 33 as shown in FIG. 11a, the lens barrel 32 is tilted as shown in FIG. 11b due to vibration.
At this time, if the lens 29 is also tilted in the same way, the image position on the sensor surface will change as indicated by the dotted line in Figure 11a.
This results in a large shift, resulting in unsightly image shaking. However, in the present invention, by using the above-mentioned material as the elastic body 30, the lens 29 does not change its position much in response to sudden vibrations.
This is because the aforementioned materials have so-called viscoelasticity, which prevents rapid deformation. Therefore, as shown by the solid line in Figure 11b,
Rapid fluctuations in the image position on the sensor surface are alleviated. Furthermore, after a certain amount of time has passed in the tilted state as shown in FIG. 11b, the position of the lens 29 gradually approaches the dotted line in the figure due to the elasticity of the elastic body. Therefore, even if the optical system suddenly vibrates or moves, the image obtained by the sensor will always move slowly, resulting in a stable image.

Although the case where there are two optical surfaces whose relative positions can be changed has been described above, it is clear that the present invention is also applicable to cases where there are a large number of optical surfaces, such as a pentaprism.

As described above, according to the present invention, two
It is possible to make a large change in the relative position of two optical surfaces, and it can be effectively used in various optical systems.

Example As shown in Fig. 12, an aluminum container 34 has a glass plate 35 with a thickness of 2 mm and an outer diameter of 50 mm in the bottom.
7 mm thick silicone rubber 36 as an elastic body.
(Product name: KE104GEL, manufactured by Shin-Etsu Chemical)
A glass plate 37 with a thickness of 2 mm and an outer diameter of 40 mm was placed on top of it. In addition, the silicone rubber 36 and the glass plate 3
Nos. 5 and 37 were adhered using a silane coupling agent. The refractive index of the glass plates 35 and 37 was 1.52, and the refractive index of the silicone rubber 36 was 1.40. As shown in FIG. 13, three permanent magnets 38, 38', and 38'' are glued onto the glass plate 37, and three electromagnets are provided below the glass plate 35, facing each other, so that the current flowing through each electromagnet is By changing the angle, the glass plate 37 could be tilted within a range of 0° to ±10°.
In this state, the bottom glass plate 3 is
When a light beam is incident perpendicularly to the glass plate 37, the deflection angle of the light beam emitted from the glass plate 37 can be varied within the range of 0° to ±4°.

[Brief explanation of the drawing]

1a and 1b are cross-sectional views of one example of the optical element according to the present invention, FIGS. 2a and 2b are cross-sectional views of other examples of the optical element according to the present invention, and FIGS. FIGS. 3b and 4 are cross-sectional views of an optical system to which the optical element of the present invention is applied, and FIG.
Figures a and 5b are cross-sectional views of another optical system using an optical element consisting of a pair of lenses holding an elastic body, and Figures 6a and 6b are cross-sectional views of another optical system using an optical element consisting of a pair of lenses holding an elastic body. 7a and 7b are cross-sectional views of other optical systems to which the optical element according to the present invention is applied, and FIGS. 8a, 8b, and 9 9a and 9b are diagrams for explaining the optical element according to the present invention in FIG. 7, FIGS. 8a and 9b are front views thereof, and FIGS. 8b and 9b are back views thereof. , FIGS. 10a and 10b are sectional views of a modification of the optical system shown in FIG. 7, and FIGS. 11a and 11b are sectional views of another optical system to which the optical element according to the present invention is applied. FIG. 12 and FIG. 13 are a sectional view and a plan view of the optical element mentioned in the example. 1,11,12,16,22,30...Elastic body, 2,3...Parallel flat glass, 4,5...Lens, 8,9,10...Parallel flat glass, 14,1
5... Lens, 17... Piezoelectric film, 20, 21...
...Parallel flat glass, 19...Objective lens, 25...
...Recording surface, 23, 23', 23''...Electromagnet, 2
4,24',24''...Ferromagnetic material, 29,31...
Lens, 32... Lens barrel, 33... Sensor surface, 3
4... Container, 35, 37... Glass plate, 36...
Silicone rubber, 38, 38', 38''...Permanent magnet.

Claims (1)

[Scope of Claims] 1. A device comprising a pair of optical members selected from lenses or flat optical members, and a light-transmitting elastic body held between the pair of optical members, and formed by the pair of optical members. An optical element characterized in that the apex angle is made variable, and the angle formed by the optical axes of the pair of optical members changes in response to a change in the apex angle. 2. An optical element comprising a pair of lenses and a light-transmitting elastic body held between the pair of lenses, wherein at least one of the lenses is configured to be movable in a direction orthogonal to an optical axis. 3. A first optical member, a second optical member, and a third optical member, all of which are arranged in a flat plate shape, and the first optical member.
a light-transmissive first elastic body held between an optical member and the second optical member;
a second light-transmissive elastic body held between the optical members, and a distance between the first optical member and the second optical member and a distance between the second optical member and the third optical member. An optical element characterized in that the dispersion properties of the first elastic body and the dispersion properties of the second elastic body are variable and different from each other. 4 A first optical member and a third optical member, both of which are plate-shaped; a curved second optical member disposed between the first optical member and the third optical member; and the first optical member.
a light-transmissive first elastic body held between an optical member and the second optical member;
a second light-transmissive elastic body held between the optical members, and a distance between the first optical member and the second optical member and a distance between the second optical member and the third optical member. An optical element characterized in that the dispersion properties of the first elastic body and the dispersion properties of the second elastic body are variable and different from each other.